Joerg Drumm

Biomechanical effect of different lumbar interspinous implants on flexibility and intradiscal pressure

Interspinous implants are used to treat lumbar spinal stenosis or facet joint arthritis. The aims of implanting interspinous devices are to unload the facet joints, restore foraminal height and provide stability especially in extension but still allow motion. The aim of this in vitro study was to compare four different interspinous implants––Colfex, Wallis, Diam and X-Stop––in terms of their three-dimensional flexibility and the intradiscal pressure. Twenty-four human lumbar spine specimens were divided into four equal groups and tested with pure moments in flexion/extension, lateral bending and axial rotation: (1) intact, (2) defect, (3) after implantation. Range of motion and the intradiscal pressure were determined.In each implant-group the defect caused an increase in range of motion by about 8% in lateral bending to 18% in axial rotation. Implantation had similar effects with all four implants. In extension, Coflex, Wallis, Diam, and X-Stop all overcompensated the instability caused by the defect and allowed about 50% of the range of motion of the intact state. In contrast, in flexion, lateral bending and axial rotation the values of the range of motion stayed about the values of the defect state. Similarly the intradiscal pressure after implantation was similar to that of the intact specimens in flexion, lateral bending and axial rotation but much smaller during extension. All tested interspinous implants had a similar effect on the flexibility: they strongly stabilized and reduced the intradiscal pressure in extension, but had almost no effect in flexion, lateral bending and axial rotation.

Implant complications, fusion, loss of lordosis, and outcome after anterior cervical plating with dynamic or rigid plates: two-year results of a multi-centric, randomized, controlled study.

Study Design. Prospective, controlled, randomized, multicenter study. Objective. To analyze implant complications and speed. Summary of Background Data. Rigid plate designs, in which the screws are locked to the plate, are in common use and thought to provide more fixation than dynamic designs, in which the screws may glide when the graft is settling. The aim of the study is to analyze (1) implant complications, (2) speed of fusion, (3) loss of lordosis, and (4) clinical outcome in both types of plates. Methods. One hundred thirty-two patients were included and assigned by randomization to one of the groups in which they received a routine anterior cervical discectomy and autograft fusion with either a dynamic plate (ABC, study group) or a rigid plate (CSLP, control group). At discharge, after 3 and 6 months and finally after 2 years, implant complications, segmental mobility, absence of radiolucencies, absence of bone sclerosis, evidence of bridging trabecular bone, loss of lordosis, Visual Analog Scale (VAS) and Neck Disability Score were recorded. All radiographic measurements were performed by an independent radiologist. Results. There have been 4 patients with implant complications within the control group and no implant complications within the study group, P = 0.045. Mean segmental mobility before discharge for the study group was 1.7 mm, 1.4 mm after 3 months, 0.8 mm after 6 months, and 0.4 mm after 2 years. For the control group, these values were 1.0, 1.8, 1.6, and 0.5 mm. The difference at 6 months between both groups was significant (P = 0.024). Neither absence of radiolucencies, nor absence of sclerosis, nor evidence of bridging bone showed significant differences between the 2 groups through the postoperative follow-up (P > 0.05). The loss of segmental lordosis for the study group with respect to intraoperative radiograph was 1.3° at discharge and 4.3° after 2 years. For the controlgroup, these values were 0.9°, 0.7°. The difference at 2 years was significant (P = 0.003). Clinical postoperative outcome (VAS and ODI) was not different between the 2 groups through the postoperative follow-up (P > 0.05). Conclusion. Dynamic cervical plate designs provide less implant complications (no patient) compared with rigid plate designs (4 patients). Speed of fusion was faster in the presence of a dynamic plate. However, loss of segmental lordosis is significantly higher if dynamic plates are used, which did not result in differences regarding clinical outcome between dynamic and constrained plates after 2 years. Thus, dynamic plates should be considered to be the preferred treatment option because of the lower risk for implant failure-related revision surgery.

Changes in Swallowing After Anterior Cervical Discectomy and Fusion With Instrumentation: A Presurgical Versus Postsurgical Videofluoroscopic Comparison

Purpose The purpose of this study was to explore the impact of anterior cervical discectomy and fusion (ACDF) with anterior instrumentation on swallowing function and physiology as measured on videofluoroscopic swallowing studies. Method We retrospectively analyzed both functional measures (penetration-aspiration, residue) and physiological/anatomical measures (hyoid excursion, posterior pharyngeal wall thickness) in a series of 17 patients (8 men, 9 women, mean age 54 years). These measures were extracted from calibrated 5-ml boluses of thin radio-opaque liquids on both pre-ACDF and post-ACDF videofluoroscopies, thus controlling for individual variation and protocol variation. Results After ACDF surgery, we found significant within-subject worsening of Penetration-Aspiration Scale (Rosenbek, Robbins, Roecker, Coyle, & Wood, 1996) scores, vallecular (but not piriform sinus) residue, superior (but not anterior) hyoid excursion, and posterior pharyngeal wall thickness. Results are discussed in the context of previous literature. Conclusions ACDF surgery can affect both physiological/anatomical and functional measures of swallowing. Future research should expand to other biomechanical and temporal variables, as well as greater bolus volumes and a wider array of viscosities and textures.

Biomechanik der interspinösen Platzhalter

Interspinous spacers are commonly used to treat lumbar spinal stenosis or facet joint arthritis. The aims of implanting interspinous devices are to unload the facet joints, restore foraminal height, and provide stability especially in extension but still allow motion. This paper summarizes several in vitro studies, which compared four different interspinous implants - Coflex, Wallis, DIAM, and X-STOP - in terms of their three-dimensional primary stability, the intradiscal pressure, and stability after cyclic loading. 24 human lumbar spine specimens were divided into four equal groups and tested with pure moments in flexion/extension, lateral bending, and axial rotation: intact, after decompression with hemifacetectomy, and after implantation. Implantation had similar biomechanical effects with all four implants. In extension, they overcompensated the instability caused by the defect and restricted extension to about 50% compared to the intact state. In contrast, in flexion, lateral bending, and axial rotation the values of the range of motion stayed similar compared to the defective state. Intradiscal pressure after implantation was similar to that of the intact specimens in flexion, lateral bending, and axial rotation but much smaller during extension; 50,000 load cycles increased the range of motion in all motion planes by no more than 20%, but in extension motion this was still less than in the intact state.

Biomechanics of interspinous spacers

Interspinous spacers are commonly used to treat lumbar spinal stenosis or facet joint arthritis. The aims of implanting interspinous devices are to unload the facet joints, restore foraminal height, and provide stability especially in extension but still allow motion. This paper summarizes several in vitro studies, which compared four different interspinous implants - Coflex, Wallis, DIAM, and X-STOP - in terms of their three-dimensional primary stability, the intradiscal pressure, and stability after cyclic loading. 24 human lumbar spine specimens were divided into four equal groups and tested with pure moments in flexion/extension, lateral bending, and axial rotation: intact, after decompression with hemifacetectomy, and after implantation. Implantation had similar biomechanical effects with all four implants. In extension, they overcompensated the instability caused by the defect and restricted extension to about 50% compared to the intact state. In contrast, in flexion, lateral bending, and axial rotation the values of the range of motion stayed similar compared to the defective state. Intradiscal pressure after implantation was similar to that of the intact specimens in flexion, lateral bending, and axial rotation but much smaller during extension; 50,000 load cycles increased the range of motion in all motion planes by no more than 20%, but in extension motion this was still less than in the intact state.

Biomechanik der interspinösen Platzhalter@@@Biomechanics of interspinous spacers

Interspinous spacers are commonly used to treat lumbar spinal stenosis or facet joint arthritis. The aims of implanting interspinous devices are to unload the facet joints, restore foraminal height, and provide stability especially in extension but still allow motion. This paper summarizes several in vitro studies, which compared four different interspinous implants - Coflex, Wallis, DIAM, and X-STOP - in terms of their three-dimensional primary stability, the intradiscal pressure, and stability after cyclic loading. 24 human lumbar spine specimens were divided into four equal groups and tested with pure moments in flexion/extension, lateral bending, and axial rotation: intact, after decompression with hemifacetectomy, and after implantation. Implantation had similar biomechanical effects with all four implants. In extension, they overcompensated the instability caused by the defect and restricted extension to about 50% compared to the intact state. In contrast, in flexion, lateral bending, and axial rotation the values of the range of motion stayed similar compared to the defective state. Intradiscal pressure after implantation was similar to that of the intact specimens in flexion, lateral bending, and axial rotation but much smaller during extension; 50,000 load cycles increased the range of motion in all motion planes by no more than 20%, but in extension motion this was still less than in the intact state.